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02 - Navigation and UI State

NavigationManager owns the typed Navigation3 back stack. MainActivity persists stable route strings in onSaveInstanceState and restores them through INavigationManager.restoreBackStack and IScreenProvider.restoreRoute. Missing features are skipped, and the start destination is prepended when restored history does not contain it.

Each retained feature provider restores its object route; detail restores its typed ID route. scaffoldFeature emits the same restoration hook for newly generated features.

ScreenRegistry rejects multiple restorers for one route and throws when no provider can render a route. Unknown routes therefore fail fast instead of silently showing a fallback.

App shell and theme

MainActivity injects IThemeManager separately from INavigationManager. Navigation no longer owns preference or theme concerns. Optional navigation observers remain multibound, allowing analytics to be removed safely.

Start flow

  • remote / offline-first: incomplete onboarding → Onboarding; then stored user → Home, no user → Login.
  • local / minimal: incomplete onboarding → Onboarding; then Home, with no auth or LoginRoute residue.

Coverage

Focused tests cover back-stack restoration, route reconstruction, duplicate restorers, unknown routes, and generated scaffold compilation. Product consumers should extend these with feature-specific ViewModel and Compose UI tests.

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